| 摘要 |
PURPOSE: To improve the purity, heat resistance, infrared scattering, heat-screening properties and homogeneity of the opaque quartz glass by filling a heat-resistant mold with 2 kinds of silicon dioxide powder different in melting point so that the surface layer is covered with the silicon oxide melting at higher temperature than the melting point of the silicon dioxide used in the core part. CONSTITUTION: A quartz glass tube 2 is inserted into the graphite mold 1 and the quartz glass tube 2 is filled with a crystalline powder of naturally occurring quartz 3 having particle sizes of 50-200μm, an average particle size of about 100μm, a bulk density of about 1.4g/cm<3> and a melting point of about 1730 deg.C. Then, the upper layer is covered with a natural quartz crystalline powder 4 having particle sizes of 50-200μm, an average particle size of about 100Mμm, a bulk density of about 1.4g/cm<3> and a melting point of 1780 deg.C in about 1cm thickness. Then, the heat-resistant mold 1 is vacuumed lower than 10<2> Torr to remove the air remaining between the quartz particles, then the vacuum is broken with a nitrogen gas. The heater 5 is turned on electricity, as a nitrogen gas is allowed flow at a rate of 5 liters/min, to raise the temperature from the room one up to 1,750 deg.C, kept at about 1,750 deg.C for 60 minutes, then cooled down to the room temperature to give an opaque quartz glass block. This block is cut to give an opaque quartz glass plate.
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